Method of making a riveted jointure

ABSTRACT

An easy opening container wall including a container wall of sheet material having a line of weakness therein defining a tear portion at least partially removable from the container wall. A hollow rivet is formed integrally with the sheet material of the tear portion and projects through an aperture of a tab. The hollow rivet is headed by a punch which forces the material making up the bead of the rivet tightly against the region of the tab immediately surrounding the aperture therein so that the area of engagement between the bead and the tab is generally annular and has substantial radial width.

Unite States Patent Brown METHOD OF MAKING A RIVETED JOINTURE Inventor:Omar L. Brown, Dayton, Ohio Assignee: Ermal C. Fraze, Dayton, OhioFiled: Nov. 4, 1969 Appl. No.: 873,829

US. Cl. ..29/509, 29/522, 113/116 FF, 113/121 C, 220/54 Int. Cl ..B2ld39/00, B23p 1 1/00 Field of Search ..29/509, 522; 220/54; 113/121C,ll6FF References Cited UNITED STATES PATENTS 3,416,221 12/1968l-lenchert ..29/522X FOREIGN PATENTS OR APPLICATIONS 590,720 7/l947Great Britain ..113/116 FF Primary Examiner-Charlie T. MoonAttorney-Smyth, Roston & Pavitt ABSIRACT An easy opening container wallincluding a container wall of sheet material having a line of weaknesstherein defining a tear portion at least partially removable from thecontainer wall. A hollow rivet is formed integrally with the sheetmaterial of the tear portion and projects through an aperture of a tab.The hollow rivet is headed by a punch which forces the material makingup the head of the rivet tightly against the region of the tabimmediately surrounding the aperture therein so that the area ofengagement between the bead and the tab is generally annular and hassubstantial radial width.

8 Claims, 6 Drawing Figures METHOD OF MAKING A RIVETED J OINTUREBACKGROUND OF THE INVENTION The invention relates to a joint betweenfirst and second members of sheet material positioned face to facewherein a portion of the first member is formed into a hollow rivet thatextends through an aperture in the second member. This type of joint iscommonly used in an easy opening container wall wherein the ho]- lowrivet is formed in a tear portion and extends through an aperture in atab that serves as manual means for severing the tear portion. A jointof this general type is disclosed, for example, in Fraze, US. Pat. No.3,191,564.

In order to form a rivet bead of requisite strength, it is necessary toextrude material of the transverse end wall of the rivet betweencooperating die surfaces during the rivet heading operation. Thisassists the radial outward flow of metal to form a head of substantialstrength. Recently rivets of this type have been made in smallerdiameters to facilitate opening of the container. In addition thealuminum alloys from which the container wall is constructed have becomeharder. These factors combine to make the need for extrusion even moreimportant in making a strong joint.

One problem with extrusion of the transverse end wall is that thesealant coating applied to the interior surface of the container wall isfractured or destroyed during the extruding operation. The sealantcoating is applied to the inner surfaces of metal containers to keep theproduct from making contact with the bare metal. Such a sealant coatingis not only tenaciously adherent to the metal but is also sufficientlyductile to survive the usual punch press operations that are required toform a can top and to join the can top to the can body. The sealantcoating will also survive the rivet forming operations as where therivet is formed in a coining operation.

The sealant coating will not, however, survive the subsequent operationof heading of the hollow rivet by squeezing the transverse end wall ofthe rivet between cooperating die members to extrude the metal radiallyoutwardly. One reason for the sealant coating rupturing inside thehollow rivet in the course of the heading operation is the high unitstress involved in drastically squeezing the sheet metal. Another reasonfor failure of the sealant coating is that the prior rivet formingoperations weaken the sealant coating. In any event, it has beendiscovered that the sealant coating inside of the hollow rivet isusually ruptured to expose bare metal to the acid action of a carbonatedbeverage within the container with consequent deterioration of thebeverage. Accordingly, the rivet heading operation which produces thestrongest rivet ruptures the sealant coating and without the extrusionof the transverse end wall the riveted jointure is not sufficientlystrong.

SUMMARY OF THE INVENTION The present invention teaches that one reasonthat prior art riveted jointures do not possess maximum strength is thatthe tab and the bead of the rivet are in substantially line contact.Specifically, the underside of the bead is generally frustoconical andthe aperture through the tab is generally cylindrical. Accordingly, theconical bead surface engages the circular rim or comer of the aperturealong a circular line which surrounds the rivet. The line contactbetween the tab and the rivet results in high stresses acting on therivet and on the region of the tab immediately surrounding the aperturetherein. Furthermore, the relatively sharp rim of the aperture may havea cutting effect on the rivet.

According to the present invention, the bearing area between the rivetand the tab is materially increased as a result of the forcing of themetal of the bead downwardly against the region of the tab immediatelysurrounding the aperture. Thus, with the present invention, the beadengages the tab in an annular region having substantial radial width.This results in reduced stress on the bead of the rivet and on theregion of the tab immediately surrounding the aperture and reduces thetendency of the rim of the aperture to cut the bead during manipulationof the tab.

Because of the increased strength of the joint as a result of the largebearing area between the bead and the tab, it is no longer necessary toextrude the material of the transverse end wall of the rivet during therivet heading operation. Thus, the sealant coacting on the inner surfaceof the transverse end wall is maintained intact throughout the rivetingoperation.

In practicing the method of this invention, the transverse end wall ofthe rivet is struck to axially collapse the rivet to cause radialoutward movement of the material of the rivet to form a bead or largerdimensions in plan than the aperture through the tab. The materialmaking up the bead is forced further toward the tab than the transverseend wall to thereby cause the bead to tightly engage the tab along anannular region which has substantial radial width.

The rivet heading operation can be advantageously carried out with apunch having a working surface with a bead forming region of the workingsurface surrounding and projecting axially of a first region of theworking surface. Preferably, the bead forming surface slopes toward thetab as it extends radially outwardly. Accordingly, the first region ofthe punch engages the transverse end wall of the rivet to cause theaxial collapse thereof. The bead forming region, being advanced axiallyof the first region, engages the material making up the bead and forcesthe latter tightly against the tab. Because the bead forming region isadvanced axially of the first region, the bead is forced closer to thetab than is the transverse end wall with the result that the undersideof the bead is forced flat against the tab.

The invention, together with further features and advantages thereof,may best be understood by reference to the following description takenin connection with the accompanying illustrative drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a top plan view of an easyopening container constructed in accordance with the teachings of thisinvention.

FIG. 2 is an enlarged fragmentary plan view of a portion of the easyopening container wall.

FIG. 3 is an enlarged fragmentary sectional view taken along line 3-3 ofFIG. 2.

FIG. 4 is a sectional view similar to FIG. 3 showing a prior art rivetedjoint construction.

FIG. 5 is an enlarged sectional view of a portion of the container walland of the hollow rivet with the hollow rivet projecting through anaperture of the tab prior to the rivet heading operation. The toolingfor use in the rivet heading operation is also illustrated in section.

FIG. 6 is a sectional view similar to FIG. with the rivet headingtooling having been advanced to form a head on the rivet.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings and inparticular to FIG. 1 thereof, reference numeral 1 1 designates an easyopening container wall constructed in accordance with the teachings ofthis invention. The easy opening container wall 11 includes a containerwall 13 constructed of aluminum or aluminum alloy and having aperipheral attaching flange 15 for attaching the easy opening containerwall 1 1 to a can body (not shown).

The container wall 13 has a line of weakness in the form of a scoreline17 therein which defines a tear portion 19 which is removable from thecontainer wall 13 to form a pouring opening. A hollow rivet 21 is formedintegrally with the sheet material of the tear portion 19 adjacent aleading end 23 of the scoreline 17. The hollow rivet 21 anchors a tab 25to the leading end of the tear portion 19. The container wall 13 may beformed with ribs 27 and 29 along opposite edges of the scoreline 19 anda large rib 31 may also be formed in the container wall.

The tab 25 is preferably constructed of sheet material such as analuminum alloy and may take the form shown in FIG. 2. In the embodimentillustrated, the tab 25 has an outer reinforcing bead 33 whichsubstantially circumscribes the tab 25 except for an end portion of thetab adjacent the rivet 21. The tab also has a generally circular innerreinforcing bead 35 which defines a generally circular finger receivingopening 37.

As shown in FIG. 3, the tab 25 has an elevated region 39 and a bottomwall or depressed region 41 with a sloping connecting wall 43 integrallyjoining the wall 41 to the elevated region 39. The elevated region 39and the connecting wall 43 completely surround the bottom wall 41. Anaperture 45 of circular configuration in plan is formed in the bottomwall 41. A planar, annular, flat surface or seat 47 on the bottom wall41 surrounds the aperture 45.

The rivet 21 anchors the tab 25 to the leading end of the tear portion19. By lifting the ring portion of the tab 25, a rupturing force istransmitted through the rivet 21 to the leading end 23 of the scoreline17 to rupture the latter. By exerting an outward pulling force on thetab 25 the tear portion 19 can be completely removed from the containerwall 13.

Before considering the characteristics and features of the rivet 21 anda preferred manner of making same, consideration should be given to atypical prior art rivet configuration shown in FIG. 4. In FIG. 4, wherecorresponding reference character followed by the letter a are used todesignate corresponding parts, a rivet 21a is formed integrally with acontainer wall 13a and projects through an aperture 45a of a tab 25a tomount the tab on the container wall. The container wall 13a may beidentical to the container wall 13 and have a scoreline 17a thereindefining a tear portion 19a in which the rivet 21a is formed. The tab25a has sharp rim or corner 49.

The rivet 21a has a transverse end wall 51, some of the material ofwhich has been extruded radially outwardly during the rivet headingoperation to form a bead 53 which extends all around the rivet 21a. Asshown in FIG. 4, the sharp corner 49 engages the frustoconical undersideof the bead 53 to define the sole region of engagement between the upperface of the tab 250 and the rivet 21a. That is, the bead 53 engages thecorner 49 and then projects upwardly away from the tab 250 so that theregion of engagement between the upper face of the tab 25a and the rivet21a is in the form of a circular line. Accordingly, when the tab 25a israised to sever the leading end of the tear portion 19a, the stress onthe corner 49 and the portion of the bead 53 engaging the corner 49 isvery high. This makes it necessary to utilize a bead having substantialdimensions and substantial strength in order to withstand the highstress. In addition, there is a danger of failure of the tab due todistortion of the sheet metal of the tab surrounding the aperture 45a.

The present invention solves the problems inherent in the constructionshown in FIG. 4 by providing a bead 55 (FIG. 3) which is clamped tightlyagainst the seat 47 over a relatively large area. Specifically, the bead55 circumscribes the aperture 45, and the area of engagement between thebead and the seat 47 is annular and has a substantial radial dimension.The bead 55 has a flat, annular, inner surface 57 which firmly engagesthe seat 47. The large area of engagement between the surfaces 47 and 57reduces the stress on the head 55 and on the bottom wall 41 so that thejoint will withstand a relatively high force applied to the tab 25during manipulation thereof to remove the tear portion 19. By comparingFIGS. 3 and 4, it can be seen that the entire bead 55 has been displaceddownwardly from the position which the bead S3 occupies. The bead 55 hasan upper or outer surface 59 which is generally annular in plan andwhich curves toward the bottom wall 41 as it extends radially outwardly.

FIGS. 5 and 6 illustrate a preferred manner of making the rivet 21. InFIG. 5, a hollow rivet 61 which has been formed integrally with theleading end of the tear portion 19 projects through the aperture 45 ofthe tab 25. The hollow rivet 61 may be formed according to knownprocesses and includes a dome-shaped transverse end wall 63 and acylindrical peripheral wall 65 integral with the end wall 63. Theperipheral wall 65 fits within the aperture 45 with a minimum amount ofclearance. The inner surface of the container wall 13 has a sealantcoating 66 adhered thereto.

A head portion 67 of a tool or support member 69 is inserted into thehollow rivet 61 to prevent radial inward collapse of the peripheral wall65 during the rivet heading operation. The head portion 67 has an endface 71 which is spaced from the transverse end wall 63.

A punch 73 having a working face 75 is suitably mounted above the rivet61. The working surface 75 has a central region 77 positioned above thetransverse end wall 63 and a peripheral bead forming region 79 whichsurrounds the central region 77. The head forming region 79 slopestoward the container wall 13 as it extends radially outwardly. Thus, theregion 79 is advanced axially of the region 77 in that it lies closer tothe tab 25 and the container wall 13 than the central region 77.Although the contour of the working surface 75 may be varied,preferably, the bead forming region 79 is arcuate in cross section andblends smoothly with the central region 77 which may be substantiallyplanar. Viewed differently, the working surface 75 is concave with theconcavity opening toward the rivet 61.

Although the portion of the working surface 75 which is formed by theplanar central region 77 can be varied, in the embodiment illustratedthe diameter of the central region 77 is preferably equal to theinternal diameter of the peripheral wall 65. Furthermore, the centralregion 77 is preferably co-axial with the rivet 61 so that the centralregion 77 terminates at lines x and y (FIG. 5) which lines extendaxially of the rivet 61 and lie along the inner surface of theperipheral wall 65. The bead forming region 79 begins at the centralregion 77 and projects radially outwardly therefrom to substantially theperiphery of the punch 73.

By relatively advancing the punch 73 and the tool 69, the central region77 will contact the transverse end wall 63 and begin to axially collapsethe rivet 61. The

axial collapse of the rivet 61 is accompanied by an outward movement ofthe metal of the rivet to begin formation of the bead 55. Ultimately,the bead will be contacted by the bead forming region 79 and displaceddownwardly thereby from the position which it would normally occupytoward the bottom wall 41. The displacement of the bead 55 causes thesurface 57 to engage the seat 47 along an area which circumscribes theaperture 45 and which has substantial width as described hereinabovewith reference to FIG. 3.

The outer surface 59 is forced axially downwardly and shaped by theregion 79. As shown in FIG. 6 the surface 59 lies axially inwardly ofthe outer surface 81 of the transverse end wall 63.

The entire rivet heading operation is carried out with little or noextrusion of the transverse wall of the rivet. As shown in FIG. 6, theend face 71 of the tool 69 is spaced from the transverse end wall 63 ofthe rivet and also spaced from the sealant coating 66. Accordingly, thesealant coating 66 remains intact throughout the entire rivet headingoperation. As shown in FIG. 3, the head portion 67 of the tool 69 iswithdrawn from the rivet subsequent to completion of the work operationshown in FIG. 6. By comparing FIGS. 5 and 6 it is readily apparent thatthe rivet heading operation does not deform the head portion 67.

Although an exemplary embodiment of the invention has been shown anddescribed, many changes, modifications, and substitutions may be made byone having ordinary skill in the art without necessarily departing fromthe spirit and scope of this invention.

Iclaim:

1. A method of joining an apertured tab of sheet material to a containerwall wherein the container wall has a line of weakness forming a tearportion and a hollow rivet with a peripheral wall and a transverse endwall is attached to the container wall and projects through the apertureof the tab, said method comprismg:

providing a punch having a working surface with the working surfacehaving a first region and a bead forming region with the bead formingregion at least substantially circumscribing the first region andtapering axially of the first region toward the container wall as itextends radially outwardly;

supporting the rivet against inward collapse by inserting a supportmember into the hollow rivet with the support member being spaced fromthe transverse end wall; relatively advancing said punch and the rivettoward each other to impact the first region of the working surfaceagainst the transverse end wall to axially collapse said hollow rivetwith consequent radial outward flow of material to form a beadintegrally joining the peripheral wall and the transverse end wall withthe relative advance of the punch and rivet causing said bead formingregion to force the bead against the region of the tab immediatelysurrounding the aperture; 7

said step of relatively advancing being carried out withoutsubstantially deforming said support member;

relatively moving the support member and the rivet to withdraw thesupport member from the rivet without destroying the rivet, thewithdrawal of the support member occurring after the formation of thebead.

2. A method as defined in claim 1 wherein said step of relativelyadvancing is carried out to cause the area of engagement between thebead and said region of the tab to be generally annular and to havesubstantial radial width.

3. A method as defined in claim 1 wherein said bead forming regiontapers smoothly toward the container wall as it extends radiallyoutwardly and correspondingly shapes the surface of the bead which itengages.

4. A method as defined in claim 1 wherein the container wall has asealant coating on the inner surface thereof and said step of relativelyadvancing is carried out without squeezing of the material of thetransverse end wall of the rivet between the support member and thepunch to thereby avoid extrusion of the material of the transverse endwall to thereby maintain the sealant coating intact during the rivetheading operation.

5. A method as defined in claim 1 wherein the inner periphery of thebead forming region is generally aligned with the inner surface of theperipheral wall prior to the axial collapse of the rivet.

6. A method as defined in claim 1 wherein said first region is generallyfiat and blends smoothly with said second region, said working surfacedefining a cavity opening toward the rivet.

7. A method of joining an apertured tab of sheet material to a containerwall wherein the container wall has a line of weakness forming a tearportion and a hollow rivet with a peripheral wall and a transverse endwall is attached to the container wall and projects through the apertureof the tab, said method comprising:

providing a punch having a working surface defining a cavity having aninner end and sloping sides which slope radially outwardly as theyextend away from the inner end, said working surface having a firstregion defining at least a portion of the inner end of the cavity and abead forming region defining at least a portion of the sides of saidcavity, said bead forming region at least substantially circumscribingthe first region;

relatively positioning the punch and the container ing:

wall so that the cavity opens toward the transverse providing a punchhaving a working surface with the end wall; working surface having afirst region and a bead supporting the rivet against radial inwardcollapse by forming region with the bead forming region at inserting asupport member into the hollow rivet 5 least substantiallycircumscribing the first region with the support member being spacedfrom the and tapering radially outwardly whereby said retransverse endwall; gions define a cavity which opens toward the rivet; relativelyadvancing said punch and the rivet toward supporting the container wall;

each other to impact the first region of the working supporting therivet against radial inward collapse by surface against the transverseend wall to initiate l inserting a support member into the hollow rivetaxial collapse of said hollow rivet with consequent With the UPPOI'I meber being Spaced from the radial outward movement of material to atleast intransverse end Wall; itiate formation of a bead with therelative advance relatively advancing said punch and the rivet to imofthe punch and rivet causing said bead forming region to engage some ofthe material of the bead and shaping the surface of the material soengaged so that said surface tapers axially away from the first regionas it extends radially outwardly whereby said surface has aconfiguration which pact the first region of the working surface againstthe transverse end wall to initiate axial collapse of said hollow rivetwith consequent radial outward flow of material to initiate formation ofa bead with the relative advance of the punch and rivet causing saidhead forming region to engage the bead and force the portion so engagedaxially of the outer surface of the transverse end wall whereby the beadis forced against the region of the tab immediately surrounding theaperture;

said step of relatively advancing being carried out without extrudingthe material of the transverse end wall; and

relatively moving the support member and the rivet to withdraw thesupport member from the rivet without destroying the rivet, thewithdrawal of the mates with the sides of said cavity; and relativelymoving the support member and the rivet to withdraw the support memberfrom the rivet without destroying the rivet, the withdrawal of thesupport member occurring after the formation of the bead. 8. A method ofjoining an apertured tab of sheet material to a container wall whereinthe container wall has a sealant coating on the inner surface thereofand a line of weakness forming a tear portion and wherein a hollow rivetwith a peripheral wall and a transverse end Support member occurringafter the formatlo of wall is attached to the container wall andprojects the bead through the aperture of the tab, said method compris-

1. A method of joining an apertured tab of sheet material to a containerwall wherein the container wall has a line of weakness forming a tearportion and a hollow rivet with a peripheral wall and a transverse endwall is attached to the container wall and projects through the apertureof the tab, said method comprising: providing a punch having a workingsurface with the working surface having a first region and a beadforming region with the bead forming region at least substantiallycircumscribing the first region and tapering axially of the first regiontoward the container wall as it extends radially outwardly; supportingthe rivet against inward collapse by inserting a support member into thehollow rivet with the support member being spaced from the transverseend wall; relatively advancing said punch and the rivet toward eachother to impact the first region of the working surface against thetransverse end wall to axially collapse said hollow rivet withconsequent radial outward flow of material to form a bead integrallyjoining the peripheral wall and the transverse end wall with therelative advance of the punch and rivet causing said bead forming regionto force the bead against the region of the tab immediately surroundingthe aperture; said step of relatively advancing being carried outwithout substantially deforming said support member; relatively movingthe support member and the rivet to withdraw the support member from therivet without destroying the rivet, the withdrawal of the support memberoccurring after the formation of the bead.
 2. A method as defined inclaim 1 wherein said step of relatively advancing is carried out tocause the area of engagement between the bead and said region of the tabto be generally annular and to have substantial radial width.
 3. Amethod as defined in claim 1 wherein said bead forming region taperssmoothly toward the container wall as it extends radially outwardly andcorrespondingly shapes the surface of the bead which it engages.
 4. Amethod as defined in claim 1 wherein the container wall has a sealantcoating on the inner surface thereof and said step of relativelyadvancing is carried out without squeezing of the material of thetransverse end wall of the rivet between the support member and thepunch to thereby avoid extrusion of the material of the transverse endwall to thereby maintain the sealant coating intact during the rivetheading operation.
 5. A method as defined in claim 1 wherein the innerperiphery of the bead forming region is generally aligned with the innersurface of thE peripheral wall prior to the axial collapse of the rivet.6. A method as defined in claim 1 wherein said first region is generallyflat and blends smoothly with said second region, said working surfacedefining a cavity opening toward the rivet.
 7. A method of joining anapertured tab of sheet material to a container wall wherein thecontainer wall has a line of weakness forming a tear portion and ahollow rivet with a peripheral wall and a transverse end wall isattached to the container wall and projects through the aperture of thetab, said method comprising: providing a punch having a working surfacedefining a cavity having an inner end and sloping sides which sloperadially outwardly as they extend away from the inner end, said workingsurface having a first region defining at least a portion of the innerend of the cavity and a bead forming region defining at least a portionof the sides of said cavity, said bead forming region at leastsubstantially circumscribing the first region; relatively positioningthe punch and the container wall so that the cavity opens toward thetransverse end wall; supporting the rivet against radial inward collapseby inserting a support member into the hollow rivet with the supportmember being spaced from the transverse end wall; relatively advancingsaid punch and the rivet toward each other to impact the first region ofthe working surface against the transverse end wall to initiate axialcollapse of said hollow rivet with consequent radial outward movement ofmaterial to at least initiate formation of a bead with the relativeadvance of the punch and rivet causing said bead forming region toengage some of the material of the bead and shaping the surface of thematerial so engaged so that said surface tapers axially away from thefirst region as it extends radially outwardly whereby said surface has aconfiguration which mates with the sides of said cavity; and relativelymoving the support member and the rivet to withdraw the support memberfrom the rivet without destroying the rivet, the withdrawal of thesupport member occurring after the formation of the bead.
 8. A method ofjoining an apertured tab of sheet material to a container wall whereinthe container wall has a sealant coating on the inner surface thereofand a line of weakness forming a tear portion and wherein a hollow rivetwith a peripheral wall and a transverse end wall is attached to thecontainer wall and projects through the aperture of the tab, said methodcomprising: providing a punch having a working surface with the workingsurface having a first region and a bead forming region with the beadforming region at least substantially circumscribing the first regionand tapering radially outwardly whereby said regions define a cavitywhich opens toward the rivet; supporting the container wall; supportingthe rivet against radial inward collapse by inserting a support memberinto the hollow rivet with the support member being spaced from thetransverse end wall; relatively advancing said punch and the rivet toimpact the first region of the working surface against the transverseend wall to initiate axial collapse of said hollow rivet with consequentradial outward flow of material to initiate formation of a bead with therelative advance of the punch and rivet causing said bead forming regionto engage the bead and force the portion so engaged axially of the outersurface of the transverse end wall whereby the bead is forced againstthe region of the tab immediately surrounding the aperture; said step ofrelatively advancing being carried out without extruding the material ofthe transverse end wall; and relatively moving the support member andthe rivet to withdraw the support member from the rivet withoutdestroying the rivet, the withdrawal of the support member occurringafter the formation of the bead.